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Glide Slope...

Old 11-06-2006, 02:09 PM
  #21  
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Lots of confusion on this topic.

According to TERPS

GlideSlope Intercept Altitude (GSIA) = The minimum (and maximum) altitude that you are authorized to intercept the glideslope/path on a precision approach (unless an alternate lower altitude is depicted and ATC clears you to that altitude for the glideslope intercept). The intersection of the published intercept altitude with the glideslope/path. The altitude and location of the lightning bolt symbol (end of feather on jepps) is the highest altitude at which glide slope can be used for primary guidance.

Final Approach Segment = shall begin at the point where the glideslope is intercepted, and designated FAF. At locations where it is not possible for the point of glideslope intercept to coincide with a designated FAF, the point of glideslope interception shall be located PRIOR to the FAF.

So yes we do have a FAF on an ILS it is GSIA. While this fix may not always be the same we have to have a FAF otherwise a part 135/121 pilot has no way to determine if the approach can continue if newly reported weather drops below minimums. (135.225 121.651)

Good discussion though.
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Old 11-06-2006, 02:38 PM
  #22  
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Well stated, and that is what I have ineptly been trying to say all along. Thanks for the post.
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Old 11-06-2006, 06:41 PM
  #23  
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Takeing time on the ILS: Just want to check this with you guys. We only take time on an ILS so that in the event that the GS goes inop we can convert to a LOC mins. If the the LOC MAP doesnt have DME then it must be time. Also this is assuming that we started time at the LOC FAF NOT GS intercept. Sound good?
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Old 11-06-2006, 08:33 PM
  #24  
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Sure, but practically speaking, if you're set for the ILS and lose the GS during the approach (inside the FAF), it's better to just go missed, set up for a non-precision approach, collect your thoughts and give it another go.

What happens if the GS goes out between the MDA and the ILS mins and how quickly will you realize it? Do you climb back up to the MDA if you're still in the soup, or just go missed? If the GS goes out, how long will it take for you to react, look at the clock, look at the plate to see the new minimums, process that mentally, double check your ground speed, reset the decision height, etc... I figure a good pilot might take 10-15 seconds, maybe more?

At 120 knots GS, in that 10-15 seconds the aircraft will travel approximately 2000-3000' and descend 50-100'. A lot can happen (in terms of approach stability) in that period, particularly for somebody that isn't 100% proficient or that's hand flying.
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Old 11-06-2006, 09:51 PM
  #25  
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Not that hard to figure out Johs, like you said you travel pretty quick at that speed and you are talking bout 200 feet difference between and MDA and DH, go missed obvioulsy, You are bloviating over this, welcome to the no spin zone.
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Old 11-06-2006, 10:24 PM
  #26  
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Common sense left this thread awhile ago....

Anyway, if the GS goes out when under the LOC MDA then it is a required missed approach. The FARs say that any time you operate under the MDA without the 3 requirements then a missed approach is required.
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Old 11-13-2006, 04:40 PM
  #27  
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If you lose the GS you must go around. You aren't magically cleared for the LOC approach if the GS fails. ATC can only clear you for one approach at a time. Not only is it the rule, but it would be stupid to suddenly change from one approach to another.
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Old 11-14-2006, 05:45 AM
  #28  
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Originally Posted by ERAU_IP406 View Post
If you lose the GS you must go around. You aren't magically cleared for the LOC approach if the GS fails. ATC can only clear you for one approach at a time. Not only is it the rule, but it would be stupid to suddenly change from one approach to another.
That is incorrect. The controller only issues you an approach clearance for the IAP title at the top of the page. Since the localizer is the non precision part of the ILS, you are cleared to fly the localizer portion any time you are "Cleared ILS". THis is true unless the controller has issued any special restrictions. Some pilots make statements like "request the localizer approach..." or "request the ILS localizer procedures". But that is technically not necessary. Either way the controller should then clear you the ILS IAP. Even if the GS is out he is supposed to clear you the ILS and advise that the GS is inop. This is all per the ATC req FAAO 7110.65 Chap 4 Sec 8.
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Old 11-14-2006, 05:50 AM
  #29  
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The other reason for identifying the nonprec FAF while on the ILS is in order to check the glideslope crossing altitude. That's the little number between the maltese cross and the NAVAID at the top. That is the only way to ensure that you are on the correct GS. There is such a phenomenon as a "false glideslope". This check is required for AF pilots BTW.
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Old 01-07-2007, 10:30 PM
  #30  
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If you lose your glide slope and you are still above LOC mins you can still complete the approach as a LOC. Thats why you should still start your clock when you cross the FAF for the LOC, if timing is how you identify the MAP.

I dont see how you think that you are switching approaches when the LOC freq is still the same for both the LOC and the ILS.

Hope your not teaching your students to go around on the ILS 7 at KDAB.
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